Sprockets on a motorcycle are toothed metal wheels designed to engage the final drive chain. Each chain-driven motorcycle features two sprockets connected by the chain. The front sprocket is much smaller and mounted on the transmission output shaft while the bigger rear sprocket is attached to the rear wheel. The transmission drives the front sprocket, which causes the chain to rotate and propel the rear wheel.
If you would like to find out more about motorcycle sprockets and gearing ratio, this post is for you.
We at PowerSportsGuide have compiled the basics of this topic under one roof!
What is a Motorcycle Sprocket?
The sprockets on a motorcycle are parts of the final drive system. While some models feature a belt or a shaft final drive, the majority of new motorcycles still utilize a chain final drive to deliver engine power to the rear wheel. A chain final drive system consists of three parts, a smaller front sprocket, a bigger rear sprocket, and the chain. These sprockets are basically metal wheels with teeth on the outer edges.
Thanks to these teeth the chain can engage the sprockets, which allows them to transmit the power.
It’s safe to say that a motorcycle’s chain drive is very similar to the drive system of bicycles.
Although a chain drive requires much more attention than alternative final drive systems (belt, shaft), they are cheaper, lightweight, and much easier to repair.
On top of that, a chain drive offers a lot of flexibility as the sprockets come in different sizes, which allows you to change your motorcycle’s gearing ratio.
Do you want to find out what a “gearing ratio” is and how to change it?
Keep reading!
What is a Gearing Ratio on a Motorcycle?
In a nutshell, the gearing ratio on a motorcycle is the ratio of size between the two sprockets. As a rule of thumb, motorcycle sprockets are measured by the number of teeth they have, and the larger the sprocket, the more teeth it has on its outer edge. The front sprocket is always about three times smaller than the rear sprocket, which reflects the number of teeth each has. This ratio reveals how fast the front sprocket can drive the rear wheel at a given RPM.
In other words, this number indicates how many times the output shaft rotates during one turn of the rear sprocket.
If you want to change the gearing ratio on your bike all you need to do is change the sprocket sizes.
Why would you do that?
For instance, if you are not happy with the stock gear ratio, you can customize your bike’s characteristics and performance based on your needs and riding style.
Let’s see how different sprocket sizes affect your bike!
What Does Changing the Sprockets on a Motorcycle do?
Changing the sprockets on a motorcycle actually changes its gearing ratio. In this way, you can adjust the bike’s top speed, acceleration, and fuel mileage. Simply put, adjusting the sprockets causes the same effect as shifting gears on a bicycle with the derailleurs. Changing the sprockets on a motorcycle is often called “gearing up” or “gearing down” depending on how the gearing ratio changes.
Installing a bigger rear sprocket or a smaller front sprocket means you are “gearing up.” In contrast, “gearing down” means using a bigger front or a smaller rear sprocket.
Are you interested in learning how these different sprocket sizes affect performance? Keep reading!
What Will a Bigger Front Sprocket do on a Motorcycle?
Simply put, a bigger front sprocket on a motorcycle lowers its gearing ratio, which is also referred to as “taller gearing.” Installing a bigger front sprocket on a motorcycle offers a higher top speed at a given engine RPM. As a side effect, these changes always lead to slower acceleration and better fuel mileage.
What Will a Smaller Front Sprocket do on a Motorcycle?
In contrast, using a smaller front sprocket on a motorcycle ensures a faster acceleration but reduces the top speed at a given engine RPM. Using a smaller front sprocket is also known as a “shorter gearing.”
What does Increasing Rear Sprocket Size do on a Motorcycle?
Surprisingly, increasing the rear sprocket size causes the same effect that decreasing the size of the front sprocket. This means that using a bigger rear sprocket results in a higher gearing ratio, which always means faster acceleration and a lower top speed.
What does a Smaller Rear Sprocket do on a Motorcycle?
Finally, a smaller rear sprocket on a motorcycle decreases the gearing ratio, which causes a higher top speed at a given RPM and better fuel consumption figures as well. On the other hand, a lower gearing ratio always means slower acceleration. This means that a smaller rear sprocket does the same job as a bigger front sprocket!
Motorcycle Gearing Ratio Chart
Since these different gearing ratios can be confusing, we’ve compiled the effects into this motorcycle gearing ratio chart:
| Front Sprocket | Front Sprocket | Rear Sprocket | Rear Sprocket | |
| Size | Smaller | Bigger | Smaller | Bigger |
| Top Speed | Slower | Faster | Faster | Slower |
| Acceleration | Faster | Slower | Slower | Faster |
| Gas Mileage | Lower | Higher | Higher | Lower |
| “Gearing” | Up | Down | Down | Up |
How do You Choose a Motorcycle Sprocket?
To choose the right motorcycle sprocket for your bike you need to consider four major factors, which are as follows:
- Material
- Size of the sprocket (number of teeth)
- Pitch (the distance between the chain’s pins)
- The thickness of the sprocket
The size of front sprockets typically ranges from 10-18 teeth, while rear sprockets usually feature 28-64 teeth. Regarding material, they are often made of steel or aluminum.
Let’s get down to the nitty-gritty and talk about each factor in detail!
Which are Better, Steel or Aluminum Sprockets?
When it comes to racing, aluminum sprockets are typically a better choice. They are much lighter than steel sprockets so they can shave a couple of pounds off the bike. The main drawback of aluminum sprockets is that they wear out faster than steel sprockets. So, if you are looking for something durable, you should consider a set of steel sprockets. They not only last longer but are generally less expensive too.
All of these are great points when it comes to everyday use!
To get the best of both worlds, some riders use an aluminum rear sprocket paired with a steel front sprocket. Why?
This is because a front sprocket needs to be more durable, so steel sprockets typically do a better job here.
But thanks to the small dimensions of front sprockets, the weight difference between the aluminum and steel sprockets is often marginal.
How do You Calculate the Motorcycle Sprocket Ratio?
Front and rear motorcycle sprockets come in different sizes, which are determined by the number of teeth they have. To calculate the motorcycle sprocket ratio, you divide the number of teeth in the rear sprocket by the number of teeth in the front sprocket. It is as simple as that! Here’s an example of a sprocket ratio calculation:
46-tooth rear sprocket with a 16-tooth front sprocket: 46/16 = 2.88
So, this means that the gearing ratio of these sprockets is 2.88, which means the first sprocket rotates 2.88 times while the rear sprocket makes one turn.
Selecting a Motorcycle Sprocket Combination
When it comes to selecting the right sprocket combination for your bike you have to be careful. Keep in mind that different types of bikes (street, dirt, AVD, cruiser, etc.) require different sprocket combinations. If you are a beginner rider, it would be best if you stick to the OEM gearing ratio, which is typically stated in the bike’s manual.
If you are not happy with the stock sprockets and want to change the performance of your bike, you may want to consider a different sprocket combination.
The degree of adjustability of your bike’s gear ratio always depends on the size of the stock sprockets.
You should avoid drastic changes in the gearing ratio, as it can dramatically affect the handling of your bike.
When replacing sprockets, the general rule is that changing one tooth on the rear sprocket causes a much smaller impact on performance.
Since the rear sprocket is about three times bigger than the front, taking off one tooth from the front virtually causes the same effect as adding three teeth on the rear.
Therefore, experts recommend that you start making changes by replacing the rear sprocket.
This allows you to make minor changes in the gearing ratio.
In contrast, adjusting the front sprocket has a much more noticeable impact on the ratio. What’s more, front sprockets feature a smaller radius, which causes the chain to turn harder.
This results in more friction, which robs engine power and leads to more wear on the chain.
Don’t forget that selecting the right sprockets for your bike is all about playing with the ratio.
This means that there are many ways to reach your goal. You can change the size of one or even both sprockets.
If you do some online research on the topic you can see that riders typically say they use “+1” or “+1/-1”, with the figures referring to the changes in the number of teeth compared to OEM sprockets.
Let’s see some examples!
According to Bike Bandit, a common sprocket adjustment on sportbikes is “-1/+2” or “-1/+3”, which translates to -1 tooth in the front sprocket and +2 or +3 teeth in the rear sprocket.
However, don’t forget that all motorcycles are different, so you have to do your own research.
But one of the easiest ways to determine the optimal sprocket sizes is to always use a sprocket chart or an online calculator.
Motorcycle Sprocket Calculators
For your convenience, we’ve gathered some of the best motorcycle sprocket calculators under one roof:
Besides the calculators, you can also find a lot of useful info on these sites!
Here’s a great video on how to use a motorcycle gearing calculator:
Motorcycle Sprocket Ratio Chart
Motorcycle sprocket ratio charts are also commonly used for comparing different gearing ratios head-to-head.
For your convenience we’ve listed the most common sprocket ratios into one chart:
This chart is for informational purposes only!
Besides using these calculators and charts, it’s highly recommended that you check your bike’s manual before you replace the sprockets. It’s also wise to contact your dealer for further advice to make an informed decision.
If you are looking for some expert tips about choosing sprockets, don’t miss this detailed post on Cycle World!
How Long Do Motorcycle Sprockets Last?
According to Solo Moto Parts, motorcycle sprockets generally last about 10,000 – 30,000 miles under ideal conditions. The life expectancy of motorcycle sprockets depends on many factors like the sprockets’ material and design, the performance of the bike, your riding style, and the quality of their maintenance. Overlooked chain maintenance or a misaligned rear wheel can significantly shorten the lifespan of sprockets!
If you ride your bike hard or in a dirty environment, you should be prepared to replace the sprockets more often.
Finally, don’t forget that stunts like wheelies or burnouts put a lot of stress on the final drive and can lead to various types of sprocket damage.
When Should You Replace Your Motorcycle Sprockets?
As a general rule, motorcycle sprockets need to be replaced if they are worn out or damaged. The most common types of motorcycle sprocket damage are as follows:
- Curved or arched teeth (“wave shape”)
- Teeth are sharp or pointed
- Unequal distance between the teeth
- The entire sprocket is warped
- Broken teeth
If the sprocket is in a good condition, the distance between its teeth should be equal. Also, the teeth should be straight with a flat surface on top.
Should You Replace Sprockets Along with the Chain on a Motorcycle?
According to RevZilla, it’s always a good idea to replace the sprockets and the chain on a motorcycle at the same time. In this way, you can be sure that the new sprockets and the chain will fit together perfectly. Running an old chain on new sprockets (or a new chain on old sprockets) wears these parts out faster.
This is because in most cases if these parts do not fit perfectly together, the chain can’t distribute the power evenly among all teeth.
What’s more, if you change the sprocket sizes significantly, you probably need a new (longer or shorter) chain anyway.
You also have to be sure that the pitch of the chain matches the sprockets.
How Long Does It Take to Change Motorcycle Sprockets?
In most cases, changing the sprockets on a motorcycle takes about 1-2 hours and requires a few special tools. To replace the rear sprocket, you have to remove the rear wheel. Even if replacing the front sprocket seems much easier, its nut is typically torqued very tight.
If you are a beginner rider, you may want to leave this replacement to a professional.
But if you’ve decided to do it by yourself at all costs make sure to refer to your bike’s manual.
How Much Does It Cost to Replace the Sprocket and the Chain on a Motorcycle?
Generally speaking, replacing the sprockets and the chain on a motorcycle costs about $80-$650. The price of a sprocket set ranges from $50 up to $250, while a new main chain can cost you anywhere from $30 to $200. If you can replace them yourself, be prepared to pay $80-$450 just for the parts. But if you take your bike to a dealer, figure another 1-2 hours of labor, which translates into $100-$200. Finally, the whole replacement may cost you about $180-$650 if you get it done by a mechanic.
Who Makes the Best Motorcycle Sprockets?
It’s safe to say that some of the best motorcycle sprocket manufacturers are as follows:
- Vortex
- Renthal
- SuperSprox
- JT Sprockets
Related Questions
What Does more teeth on a motorcycle sprocket mean?
More teeth on a motorcycle sprocket means that it has a larger diameter, so there will be more teeth on its outer edge.
What does a bigger sprocket do on a motorcycle?
Using a bigger sprocket on a motorcycle changes its gearing ratio. Simply put, a bigger front sprocket means a higher top speed but slower acceleration, while a bigger rear sprocket causes the bike to accelerate faster but leads to a lower top speed.
Does a smaller front sprocket make a motorcycle go faster?
A smaller front sprocket on a motorcycle results in a lower top speed. On the other hand, it causes the bike to accelerate faster!
Does a smaller rear sprocket make you go faster?
Yes, a smaller rear sprocket makes a motorcycle go faster but it also causes the acceleration to decrease.
What sprocket is best for speed?
For the highest top speed, you need a bigger front sprocket or a smaller rear sprocket.
Are motorcycle sprockets universal?
No. Unfortunately, motorcycle sprockets are not universal. Unlike chains, motorcycle sprockets are always bike-specific!
How do you calculate motorcycle gear ratios?
To calculate the gear ratio of a motorcycle you have to simply divide the number of teeth in the rear sprocket by the number of teeth in the front sprocket.
Are JT Sprockets any good?
Yes, JT Sprockets are known for their high quality, durability, and affordable price tags. That’s why JT Sprockets is one of the most well-known OEM suppliers!
Conclusion
When it comes to the final drives of motorcycles, we can distinguish between the belt, shaft, and chain final drive systems.
It’s safe to say that that chain drive is still by far the most popular, and with good reason.
The chain and sprockets are cheap, lightweight, and easy to replace. That’s why this system is still commonly used on virtually all types of motorcycles.
Regarding its design, every chain-driven motorcycle features two sprockets, which are connected to a metal chain. These sprockets come in many shapes and materials.
The front sprocket is always significantly smaller than the rear and is often referred to as a “drive sprocket.” This sprocket typically has only 13-18 teeth.
In contrast, the rear sprocket, which is also known as a “driven sprocket” is much larger, as it usually has 28-62 teeth.
Changing the size of the sprockets actually changes the gearing ratio, which is the easiest way to adjust the performance of a motorcycle.
The general rule is that a smaller front sprocket or a bigger rear sprocket results in a faster acceleration but slower top speed. In contrast, a larger front sprocket or a smaller rear sprocket increases the top speed but causes a decrease in acceleration.
References:
https://www.bikebandit.com/blog/how-to-choose-motorcycle-sprockets
https://www.cycleworld.com/sport-rider/free-horsepower-for-taking/
https://www.solomotoparts.com/blog/Aluminum-v.-Steel-Motorcycle-Sprockets
https://www.motorcyclistonline.com/gearing-changes-explained/
